The present invention relates to a viscous material application apparatus for applying a viscous material such as an adhesive, cream solder or a conductive paste to an application target such as a circuit board.
The basic configuration of a conventional viscous material application apparatus is described with reference to the schematic illustrations of FIG. 29A and FIG. 29B. As shown in FIG. 29A, this viscous material application apparatus comprises a material supply section 1 for holding a viscous material 5 such as an adhesive or cream solder, and a pressure regulating section 22 for regulating and supplying compressed air to the material supply section 1, and the viscous material 5 is pressurized by the compressed air, and discharged from a discharge port 4a of a discharge section 4.
Furthermore as shown in FIG. 29B, in some cases a valve 16 for starting and stopping the supply of compressed air may also be provided between the material supply section 1 and the discharge section 4. In this apparatus, in the case where a predetermined quantity of the viscous material 5 is required to be discharged, the viscous material 5 is pressurized from above by compressed air supplied from the pressure regulating section 22 and forced downward, and the valve 16 is then opened and the viscous material 5 discharged from the discharge port 4a. Then, when application onto the circuit board has been completed, the valve 16 is closed.
However, in a viscous material application apparatus of the conventional configuration described above, because the compressed air supplied from the pressure regulating section 22 is applied on top of the viscous material 5 contained in the material supply section 1, then depending on the characteristics of the viscous material 5, the pressure of the compressed air may be affected by the viscosity resistance of the viscous material 5 and find it difficult to reach the vicinity of the distant discharge port 4a of the discharge section 4. Consequently, variations developed in the pressure transmission, and it was difficult to obtain highly accurate discharge quantities and discharge pressures.
Furthermore as shown in FIG. 30, the response time from the point where a signal is output to start discharge at a predetermined pressure, to the point where discharge at that pressure is actually started, also lengthens for the same reasons, and so a waiting period develops from transmission of a discharge start signal to the actual start of discharge. In addition, after stopping pressurization residual pressure remains, and so other problems arise such as the viscous material 5 hanging down from the discharge port 4a being forced out near the discharge port 4a and adhering to the circuit board, creating a bridge, when the viscous material application apparatus is next positioned on the circuit board.
Furthermore in the aforementioned conventional apparatus, in those cases where a device called a multiple nozzle 4c with a plurality of discharge ports 4d, such as that shown in FIG. 31A and FIG. 31B, was used for performing a two dimensional bulk supply of the viscous material, the following problems also arose. In highly viscous materials, the pressure transmission through to the viscous material 5 does not occur uniformly, and when a conductive paste 31 was applied to a circuit board 32, then as shown in FIG. 32A and FIG. 32B, because the transmitted pressure from the compressed air differed depending on the position of the discharge port 4d, a variation developed in the discharge quantity depending on the discharge position.
The present invention aims to resolve the above problems, with an object of providing a viscous material application apparatus capable of improving discharge accuracy and increasing efficiency by carrying out the pressure transmission for discharging the viscous material efficiently, and improving the responsiveness.
In order to achieve the above object, a viscous material application apparatus of the present invention comprises: a main body having a pressurized chamber which connects through to a discharge port and stores a viscous material; and a viscous material supply device for transferring the viscous material under pressure to the pressurized chamber, wherein a discharge pressure regulating device for regulating the discharge pressure of the viscous material by increasing or decreasing the capacity of the pressurized chamber when the viscous material inside the pressurized chamber is pressurized and discharged is provided either inside the pressurized chamber or facing the pressurized chamber.
According to the present invention, because the viscous material stored in the pressurized chamber is discharged with a discharge pressure regulated by the discharge pressure regulating device provided either inside the pressurized chamber or facing the pressurized chamber, the air pressure is transmitted efficiently and uniformly to the viscous material, and so the responsiveness from the start of pressurization to the start of discharge improves, and a suitable discharge quantity of the viscous material is discharged almost instantaneously. Then, following completion of the discharge, because no residual pressure remains within the pressurized chamber, the problem seen in conventional apparatus, where the viscous material hangs down from the discharge port and then adheres to the application target during the next application, is prevented. Because the effects of viscosity resistance are minimal even with highly viscous materials, improved discharge accuracy and increased efficiency are achieved across all types of viscous material application, enabling for example, a uniform discharge even in the case of screen printing where a printing paste is applied along a straight line.
The discharge pressure regulating device may suitably comprise a pouch positioned inside the pressurized chamber for increasing or decreasing internal capacity thereof through the intake or exhausting of gas, and an air supply section for regulating the pressure inside the pouch by either supplying gas to, or discharging gas from the pouch, and as the shape of the pouch transforms with the intake or exhausting of gas from the air supply section and the pressurized chamber, the capacity of the pressurized chamber is increased or decreased, enabling the discharge pressure to be easily adjusted. In this case, the closer the air pouch is positioned to the discharge port inside the pressurized chamber, the smaller the difference will be between the air pressure used for discharge and the actual discharge pressure, and the more the responsiveness is improved.
The discharge pressure regulating device may also be constructed from an actuator such as an air cylinder and a voice coil motor, and a diaphragm which transforms under the influence of the actuator and increases or decreases the capacity inside the pressurized chamber.
Furthermore, it is desirable to employ a configuration in which a pressurized chamber, a discharge pressure regulating device and a discharge port are shared across a plurality of linearly aligned viscous material supply devices, with the discharge pressure of the viscous material at discharge positions along the alignment direction of the viscous material supply devices being regulated in a single batch. According to this configuration, in screen printing such as that described above, the discharge of a highly viscous printing paste is carried out uniformly and with a high degree of accuracy, regardless of the discharge position.
Another suitable configuration uses a plurality of discharge pressure regulating devices, with the discharge pressure of the viscous material at a discharge position being regulated as desired, and this configuration enables localized pressure regulation to be performed with ease.
Furthermore, by attaching a pair of inclined plates which approach one another in a downward direction to both sides of the lower section of the pressurized chamber, and using the opening between the bottom edges of these plates as a discharge port, these inclined plates function as a substitute for a squeegee in the aforementioned screen printing, and enable the filling of a screen opening with printing paste to be appropriately performed by discharge pressure regulation, and so highly accurate printing is possible, and an improvement in printing quality is achieved.
According to a configuration not restricted to supply by pressure transfer using the viscous material supply device used for transferring the viscous material under pressure in the aforementioned configuration, by forming the main body to allow for easy exchange, and enabling a cartridge filled with a viscous material to be accommodated within the main body, the viscous material is stored in the pressurized chamber, the pressurizing device for supplying the viscous material becomes unnecessary, and supply of the viscous material is simplified.
Furthermore in another suitable configuration, a soft elastic material is inserted between the aforementioned inclined plates and the lower side surfaces of the pressurized chamber. In such a configuration, when the inclined plates are pressed onto the screen, the inclined plates flex causing an improvement in the adhesion with the screen. Accordingly, the problem of the viscous material seeping out between the inclined plates and the screen when the viscous material is supplied into the pressurized chamber or when the viscous material inside the pressurized chamber is pressurized is prevented. However, in order to further improve the adhesion, the inclined plates need to be lengthened to increase their flexion. Such lengthening causes the capacity of the pressurized chamber to increase and the amount of supplied viscous material to increase, which leads to an increase in the supply time and an increase in the weight of the application unit. By inserting a soft elastic material between the inclined plates and the lower side surfaces of the pressurized chamber, the capacity of the pressurized chamber is kept small while still ensuring flexion of the inclined plates, and the volume of the viscous material is kept to a minimum. The soft elastic material could also be constructed along the inclined plates, and may be connected at the edges of the two plates, or alternatively separate pieces of soft elastic material are also inserted at the edges of the inclined plates. When large amounts of viscous material are permissible, the soft elastic material need not be formed along the inclined plates, and a soft material could be inserted only at the tips of the inclined plates.
In another suitable configuration, in the case where following the filling of the pressurized chamber with a viscous material using the aforementioned viscous material supply device the supply pressure of the viscous material supply device is cut, but even though the supply pressure has been cut the viscous material within the pressurized chamber still retains a degree of pressure, a pouch which functions as a discharge pressure regulating device absorbs this residual supply pressure remaining in the pressurized chamber, causing a reduction in the pressure inside the pressurized chamber. Accordingly, the residual pressure within the pressurized chamber is removed, and the discharge pressure is controlled using the aforementioned pouch.
Furthermore, in another suitable configuration, by providing a pressure detecting member at an internal edge of the pressurized chamber or between the pressure chamber and the viscous material supply device, then as the viscous material is supplied to the pressurized chamber by the viscous material supply device, the pressure detecting member detects when the pressurized chamber is full of the viscous material.
Furthermore in another suitable configuration, in those cases where during pressurization of the pressurized chamber by the discharge pressure regulating device, the detected pressure at pressure detecting member does not reach a predetermined pressure, a judgment is made that the amount of viscous material is insufficient, and the viscous material supply device is used to supply the viscous material to replenish the viscous material within the pressurized chamber.
In another suitable configuration, the pressurized chamber is moved while pressurized by the discharge pressure regulating device, and the pressure of the discharge pressure regulating device is regulated based on a pressure of the pressurized chamber detected with the pressure detecting member.
Furthermore in another suitable configuration, a rotatable shaft is provided in the pressurized chamber, and the viscous material is mobilized by rotating the shaft.
Furthermore in another suitable configuration, the viscous material is recovered into the pressurized chamber by setting the pressure of the pressurized chamber to a negative pressure by the discharge pressure regulating device following completion of discharge, and lifting the pressurized chamber while moving the chamber in a horizontal direction.
Moreover in another suitable configuration, the temperature of the viscous material is stabilized by exchanging the air inside an air pouch.